San Francisco-based Sensor Tower is one of those. They’ve just closed a $1 million round of funding to deploy an app analytics service that tells developers how they might improve keywords in their apps’ descriptions.

Rembrandt Ventures led the round, which also included Merus Capital, Bertelsmann Digital Media Investments, Pejman Nozad, Mar Hershenson, Ariel Poler and Maneesh Arora. They were part of the AngelPad’s 2013 class. They’ll use the round to improve the Android version of the service and hire employees.

Both co-founders, Oliver Yeh and Alex Malafeev, are app developers. They found that the cost to acquire new users — often at $1 or more (or even several dollars per user) — was too expensive. They started building Sensor Tower as their own personal tool and then opened it up to third-party developers.

You can test drive how Sensor Tower works by typing the name of your application into the search bar on their homepage here. It shows which keywords pop up for a given app, and can tell a developer how well they rank for each keyword.

The company naturally has a freemium model where they charge anywhere from $39 to $399 per month based on the number of keywords and apps a developer wants to track. The startup is profitable with about 10,000 developers using the service, including clients like Skype, GREE and Flipboard.

These plans give developers data on how well their apps rank in given categories and for given keywords over a historical period of time. Sensor Tower also automatically generates a list of relevant competitors based on keywords.